The present invention relates to low profile hacksaws and, more particularly, to low profile hacksaws with an elongated I-beam frame member.
Conventional hacksaws typically comprise a blade, a handle, and a metal frame member which extends forwardly from the handle parallel to the blade and then bends 90 degrees so as to extend downwardly. A tensioning device is provided on the lower portion of the handle and the blade is mounted and tensioned between the tensioning device and the lower forward end of the frame.
The overall configuration of this type of hacksaw is generally rectangular. This conventional construction has two significant shortcomings. First, the tension applied to the blade creates a bending moment in the frame member which is focused at the portion forming the 90 degree bend. When enough tension is applied, the frame tends to deform at the bend and may remain in a deformed state if the metal material goes beyond its yield point at the bend. Second, the overall distance between the blade and the upper portion of the frame member makes the hacksaw unsuitable for use in tight openings or other difficult to access areas.
Hacksaws with forwardly and downwardly sloped frames have been provided in the art. The sloped configuration of these frames allows the forward end of the hacksaw to be positioned in tight openings and other places that are difficult to access. The increased height towards the rear of these sloped hacksaws is desirable to allow the hacksaw to cut through large work pieces without having the frame overly limit the depth to which the saw can cut. An example of such a hacksaw is shown in U.S. Pat. No. 3,329,186. The hacksaw of the ""186 patent, however, has a sharp bend towards the forward end thereof. Thus, although the sloped configuration of the hacksaw of the ""186 patent allows it to be utilized in tighter areas than most hacksaws, the tension load applied by the blade will be focused on the sharp bend. This focused or concentrated load may cause permanent deformation at the sharp bend if sufficient tension is applied to the blade.
It is therefore an object of the present invention to provide a hacksaw with an improved frame arrangement wherein the tension load applied to the frame by the blade is distributed along the frame to prevent focusing or concentration of the load at one particular point thereof. To achieve this object, the present invention provides a low profile hacksaw comprising an elongated blade having a cutting edge. A hacksaw frame assembly comprises a rigid I-beam frame member that has a forward end portion and a maximum height portion. Preferably, the maximum height portion is located at the rear end of the frame member, but it may be located intermediate the forward and rearward ends. The frame member has an arcuate portion which extends substantially the entire length between the forward end and maximum height portions and which curves downwardly and forwardly towards the forward end portion to provide the hacksaw with a low profile. The hacksaw frame assembly further comprises a manually engageable handle for manual grasping to enable performance of a cutting operation wherein the cutting edge of the tensioned blade is engaged with a work piece and moved forwardly and rearwardly to cut through the work piece. A releasable blade tensioning device provides a second blade mounting structure on which the other longitudinal end portion of the blade is removably mounted. The blade tensioning device is constructed and arranged to affect relative tensioning movement between the first and second blade mounting structures to tension the blade in the longitudinal direction thereof. One of the first and second blade mounting structures is provided on the forward end portion of the frame member such that the tension in the blade applies a rearwardly directed load to the forward end portion to create a bending moment which is distributed along the arcuate portion.
As a result of providing the frame with a curved arcuate portion between its forward end portion and maximum height portion, the rearwardly directed load applied by the tensioned blade is distributed throughout the frame as a bending moment. Preferably, the arcuate portion is defined along at least one arc which has its center of curvature located below the blade. This preferred arrangement is advantageous because it ensures that the arcuate portion extends over a sufficient distance whereby the bending moment will not be focused at a particular point. It is to be understood that the frame member of the present invention may be composed of a number of interconnected arcuate portions each having different centers of curvature. However, it is preferred that the upper and lower I-beam end caps extend along the circumferences of two imaginary circles which have their centerpoints located below the blade and thus have constant radii. This arrangement has been found to provide optimal stress distribution in this type of arrangement. Preferably, the imaginary circles have different centerpoints.
The use of an I-beam in this construction is particularly advantageous because the I-beam provides the frame with increased rigidity without increasing the overall weight of the hacksaw. Specifically, an I-beam frame member of a given weight has a greater resistance to bending as a result of a substantial part of the mass being located at the upper and lower end caps in comparison to a square or cylindrical beam of the same weight.
The blade tensioning device is preferably the handle-mounted pivotal type which is disclosed in the present application. However, any one of a variety of tensioning devices may be used in its place. For example, the tensioning device could be provided at the forward end portion of the frame rather than on the handle. The tensioning device could also have a conventional threaded wing nut-type arrangement. Thus, it can be appreciated that the tensioning device used in the hacksaw of the present invention may be of any type, and is not limited to the disclosed embodiment.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.